nierzadko

In a sentence

• Nierzadko odwiedza nas jego mama.

  His mother visits us quite often.

  In this sentence, 'nierzadko' is used to indicate that the event of the mother visiting occurs quite frequently, though not always.

• Występy tego artysty są nierzadko wyjątkowe.

  This artist's performances are often extraordinary.

  Here, 'nierzadko' emphasizes that in many instances, the artist's performances have been remarkable.

• Nierzadko zdarza się, że pogoda zmienia się nagle.

  It is not uncommon for the weather to change suddenly.

  In this example, 'nierzadko' is used to state that it is relatively frequent or a regular phenomenon for weather changes to occur suddenly.